Therapeutic antibodies against ROR-1 protein and methods for use of same

ABSTRACT

Therapeutic antibodies having binding specificity for ROR-1 expressed on cancer cells (particularly leukemic and lymphomic cells) and pharmaceutical compositions containing one or more such antibodies for use in treating cancer. Methods for diagnosing such cancers through in vitro detection of binding to ROR-1 protein expressed on putative cancer cells are also provided.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No. 14/846,400, filed Sep. 4, 2015, which is a continuation of U.S. patent application Ser. No. 13/997,934, filed Jun. 27, 2013, now issued as U.S. Pat. No. 9,217,040, which is a national stage entry of International Patent Application No. PCT/US2012/021339, filed Jan. 13, 2012, which claims the benefit of U.S. Provisional Patent Application No. 61/433,043, filed Jan. 14, 2011, each of which is incorporated herein by reference in its entirety and for all purposes.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

This invention was made with government support under NIH CA081534 awarded by The National Institutes of Health. The government has certain rights in the invention.

BACKGROUND

Tyrosine kinases are important mediators of the signaling cascade, determining key roles in diverse biological processes like growth, differentiation, metabolism and apoptosis in response to external and internal stimuli. Studies have implicated the role of tyrosine kinases in the pathophysiology of cancer. Schlessinger J. (2000) Cell, 103:211-225; and Robinson et al. (2000) Oncogene, 19:5548-5557. MacKeigan and colleagues used a large-scale RNAi approach to identify kinases that might regulate survival and apoptosis of a human tumor cell line (HeLa), RNAi to ROR1 was found as one of the most potent in inducing apoptosis among the set of RNAi targeting each of 73 different kinase-encoding genes. MacKeigan et al. (2005) Nat Cell Biol., 7:591-600. However, these investigators did not examine the expression or function of ROR1 protein in these cells.

ROR1, receptor tyrosine kinase like orphan receptor one, is a molecule expressed at high levels during embryogenesis that plays a major role in the development of the skeleton, lungs and nervous system. ROR1 expression is greatly decreased in postpartum mammalian cells to levels that are barely detectable. ROR1 is a membrane-receptor with an intracellular kinase-like domain and extracellular Frizzled-like cysteine-rich domain, which is common to receptors of members of the Wnt-family. ROR1 is member of the ROR family that is evolutionarily conserved among Caenorhavditis elegans, Drosophila, mice and humans. Wilson C, Goberdhan D C, Steller H. Dror, a potential neurotrophic receptor gene, encodes a Drosophila homolog of the vertebrate Ror family of Trk-related receptor tyrosine kinases. Proc Natl Acad Sci USA. 1993; 90:7109-7113; Oishi et al. (1997) J Biol Chem., 272:11916-11923; Masiakowski et al. (1992) J Biol Chem., 267:26181-26190; Forrester et al. (2002) Cell Mol Life Sci., 59:83-96; and Oishi et al. (1999) Genes Cells, 4:41-56. The actual functional role of the ROR1 protein during embryogenesis is unknown, although it is believed to be a receptor for Wnt proteins that regulate cellular polarity and cell-to-cell interactions.

Although principally an embryonic protein, ROR1 is expressed uniquely on certain cancer cells, including in CLL, small lymphocytic lymphoma, marginal cell B-Cell lymphoma, Burkett's Lymphoma, and other cancers (e.g., breast cancers), but not on normal adult tissues and cells. In a recent study, it was found that ROR1, at both mRNA and protein level, was highly expressed in CLL B cells but not normal B cells. Moreover, it was found that ROR1 is a receptor for Wnt5a, which could induce activation of NF-κB when co-expressed with ROR1 in HEK293 cells and enhance survival of CLL cells in vitro. This indicates that ROR1 is a CLL survival-signaling receptor for Wnt5a. Another study found that ROR1 was expressed in acute lymphocytic leukemia (ALL) as well. Shabani et al. (2007) Tumour Biol., 28:318-326; and Baskar et al. (2008) Clin Cancer Res., 14:396-404. Expression of ROR1 protein has now been demonstrated on a variety of hematologic and solid tumor cancers.

Therapeutic control of ROR1 expression is necessary. However, although polyclonal anti-ROR1 antibodies raised against ROR1 peptide are commercially available. The inventors developed a monoclonal anti-ROR1 antibody, terms 4A5, which reacts with the native ROR1 protein and is capable of detecting cell-surface expression of ROR1 for flow cytometric analysis. However, robustly therapeutic antibodies with demonstrable ability to inhibit ROR-1 mediated cancer cell proliferation to a degree that is therapeutically significant for slowing or preventing growth and metastasis have not been available.

SUMMARY OF THE INVENTION

The invention provides antibodies and combination of antibodies for in vivo and in vitro inhibition of ROR-1 cell mediated proliferation of cells from subjects with cancer, including lymphomas, CLL, small lymphocytic lymphoma, marginal cell B-Cell lymphoma, Burkett's Lymphoma, renal cell carcinoma, colon cancer, colorectal cancer, breast cancer, epithelial squamous cell cancer, melanoma, myeloma, stomach cancer, brain cancer, lung cancer, pancreatic cancer, cervical cancer, ovarian cancer, liver cancer, bladder cancer, prostate cancer, testicular cancer, thyroid cancer, and head and neck cancer, but not in blood or splenic lymphocytes of nonleukemic patients or normal adults.

The antibodies of the invention are also useful for differentiation between ROR1 expressing cancer cells (“ROR1 cancer”) and normal cells. For example, an immunoassay that detects ROR1 in a sample from a subject by contacting the sample with a ROR1-specific antibody of the invention and detecting immunoreactivity between the antibody and ROR1 in the sample is provided.

In accordance with a further aspect of the invention, a ROR1 cancer is diagnosed in a subject by detecting the presence or quantity of ROR1 protein in a sample.

The present invention includes compositions that include purified, isolated monoclonal antibodies and combinations thereof that bind specifically to ROR1 receptor protein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a series of graphs illustrating the results of flow cytometric analysis of the expansion of CD5+B220low leukemia B cells in ROR1 Tg mice following the adoptive transfer of 1×10⁷ splenocytes from a ROR1×TCL1 Tg mouse. Upper panel depicts the expansion from 2 to 4 weeks following adoptive transfer. Percentage of leukemic cells on the contour plot of mCD5 (x-axis) vs mB220 (y-axis) is indicated on above the gate on CD5⁺B220^(low) lymphocytes. Bottom panel depicts the relative ROR1 expression (x axis) using the mouse anti-ROR1 4A5 mAb.

FIG. 2 is a diagram outlining the analysis of anti-ROR1 mAb on the adoptive transfer and engragment of ROR1×TCL1 leukemic splenocytes. ROR1 Tg mice (4 mice/group) were given 250 ug of 4A5, D10 or control mIgG i.v. on day 0. The following day, 1×10⁷ splenocytes from a ROR1×TCL1 Tg mouse were adoptively transferred i.v. All mice were subsequently monitor weekly for expansion of CD5⁺B220^(low) leukemic B cells by flow cytometry beginning at 2 weeks post transfer.

FIG. 3 is a series of graphs illustrating the results of a flow cytometric analysis which demonstrate that anti-ROR1 antibodies of the invention inhibited the development of CLL-like leukemia in ROR1 Tg mice. 2 weeks after adoptive transfer, the PBMC facs analysis were performed. The data showed the anti-ROR1 antibody D10 but not anti-ROR1 antibody 4A5 could markedly inhibit the CD5^(dull)B220⁺ and ROR1^(bright)B220⁺ leukemic B cell expansion.

FIG. 4 panels A and B show a series of graphs illustrating the results of in vivo testing in a murine model of human breast cancer. The anti-ROR1 antibodies inhibited breast cancer metastasis in rag−/− g−/− deficiency mice. 5E5 MDA-MB-231 breast cancer cell were transferred by i.v. injection to rag−/− g−/− mice on day 1. The rag−/− g−/− deficiency mice were also i.v. injected isotype control or anti-ROR1 antibody (4A5, D10, and 4A5 plus D10) on day 1, 3, 7 and 14 at 100 mg per mice. FIG. 4 (center panel) also provides images from IVIS in vivo imaging procedures on the above mice, which were performed every week. 5 weeks later, the mice were sacrificed and histology analysis were performed (FIG. 4 panel B). The anti-ROR1 antibody D10 and the antibody combination (4A5 plus D10) both significantly inhibited metastasis of the breast cancer, with inhibition by D10 alone being greater than inhibition by 4a5 alone.

FIG. 5 provides a nucleotide coding sequence comparison of 4A5 Ig heavy chain (VH) to the closest germline mouse and human immunoglobulin (Ig) VH.

FIG. 6 provides a nucleotide coding sequence comparison of G6 Ig heavy chain (VH) to the closest germline mouse and human immunoglobulin (Ig) VH.

FIG. 7 provides a nucleotide coding sequence comparison of G3 Ig heavy chain (VH) to the closest germline mouse and human immunoglobulin (Ig) VH.

FIG. 8 provides a nucleotide coding sequence comparison of H10 Ig heavy chain (VH) to the closest germline mouse and human immunoglobulin (Ig) VH.

FIG. 9 provides a nucleotide coding sequence comparison of D10 Ig heavy chain (VH) to the closest germline mouse and human immunoglobulin (Ig) VH.

FIG. 10 is a diagram and chart depicting the highly conserved nature of human and murine ROR1.

FIG. 11 is a nucleotide comparison depicting the domain structure and sequence homology of human and murine ROR1 extracellular protein.

FIG. 12 is a chart indicating the extracellular domain which the anti-ROR1 mAbs bind the ROR1 protein.

FIG. 13 is a diagram depicting the chimeric ROR1 proteins generated to determine the binding domain of each of the anti-ROR1 mAbs.

FIG. 14 is a diagram depicting the truncated ROR1 proteins generated to determine the sub-regions which each of the anti-ROR1 mAbs binds.

FIG. 15 is a diagram depicting the amino acids which were murinized to determine residues critical for mAb binding to human ROR1 and a western blot showing that the 138 glutamic acid residue is critical for antibody D10 binding to human ROR1.

FIGS. 16A-16B are graphs indicating the K_(D) values for antibody D10 (FIG. 16A) and 4A5 (FIG. 16B).

FIG. 17 is a series of graphs illustrating the anti-ROR1 antibody D10 is highly active in in vivo assays.

FIG. 18 is a diagram outlining the analysis of anti-ROR1 mAb on the adoptive transfer and engragment of ROR1×TCL1 leukemic splenocytes. ROR1 Tg mice (5 mice/group) were given 250 ug of 4A5, D10 or control mIgG i.v. on day 0. The following day, 5×10⁵ splenocytes from a ROR1×TCL1 Tg mouse were adoptively transferred i.v. All mice were subsequently monitored weekly for expansion of CD5^(dull)B200⁺ leukemic B cells by flow cytometery beginning at 2 weeks post transfer.

FIG. 19 a series of graphs illustrating the results of flow cytometric analysis of the anti-ROR1 antibodies inhibiting the development of CLL-like leukemia in ROR1 Tg mice. 2 weeks after adoptive transfer, the PBMC facs analysis were performed. The data showed the anti-ROR1 antibody D10 but not anti-ROR1 antibody 4A5 could markedly inhibit the CD5^(dull)B220⁺ and ROR1^(bright)B220⁺ leukemic B cell expansion.

FIG. 20 is a graph illustrating that anti-ROR1 antibody D10 inhibits the development and expansion of ROR1×TCL1 leukemic B cells in the blood of recipient animals until two weeks after receiving the last infusion of the mAb.

FIG. 21 is a depiction of the rapid internalization of the anti-ROR1 antibody D10 into CLL cells.

FIG. 22 is a series of graphs illustrating the results of flow cytometric analysis showing that anti-ROR1 antibodies D10 and 4A5 are both internalized into CLL cells. CLL cells were incubated with mouse anti-hROR1 Ab-Alex647 for 30 min at 4° C. Subsequently the cells were washed and either left at 4° C. or incubated for 4 hours at 37° C., followed by flow cytometry. The background signal with non-staining is also shown.

FIG. 23 is a graph illustrating the kinetics of the internalization of anti-ROR1 antibodies D10 and 4A5.

FIG. 24 is a diagram depicting the amino acids which were murinized to determine residues critical for mAb binding to human ROR1 and a western blot showing that the 111 isoleucine residue is critical for antibody 4A5 binding to human ROR1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The presently disclosed subject matter are described more fully below. However, the presently disclosed subject matter may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Indeed, many modifications and other embodiments of the presently disclosed subject matter set forth herein will come to mind to one skilled in the art to which the presently disclosed subject matter pertains having the benefit of the teachings presented in the foregoing descriptions and the associated FIGS. Therefore, it is to be understood that the presently disclosed subject matter is not to be limited to the specific embodiments disclosed and that modifications and other embodiments are intended to be included within the scope of the appended claims.

Antibodies of the invention were produced monoclonally using techniques as previously described. Briefly, Naturally occurring antibodies are generally tetramers containing two light chains and two heavy chains. Experimentally, antibodies can be cleaved with the proteolytic enzyme papain, which causes each of the heavy chains to break, producing three separate subunits. The two units that consist of a light chain and a fragment of the heavy chain approximately equal in mass to the light chain are called the Fab fragments (i.e., the antigen binding fragments). The third unit, consisting of two equal segments of the heavy chain, is called the Fc fragment. The Fc fragment is typically not involved in antigen-antibody binding, but is important in later processes involved in ridding the body of the antigen.

Because Fab and F(ab′)₂ fragments are smaller than intact antibody molecules, more antigen-binding domains are available than when whole antibody molecules are used. Proteolytic cleavage of a typical IgG molecule with papain is known to produce two separate antigen binding fragments called Fab fragments which contain an intact light chain linked to an amino terminal portion of the contiguous heavy chain via by disulfide linkage. The remaining portion of the papain-digested immunoglobin molecule is known as the Fc fragment and consists of the carboxy terminal portions of the antibody left intact and linked together via disulfide bonds. If an antibody is digested with pepsin, a fragment known as an F(ab′)₂ fragment is produced which lacks the Fc region but contains both antigen-binding domains held together by disulfide bonds between contiguous light and heavy chains (as Fab fragments) and also disulfide linkages between the remaining portions of the contiguous heavy chains (Handbook of Experimental Immunology. Vol 1: Immunochemistry, Weir, D. M., Editor, Blackwell Scientific Publications, Oxford (1986)).

As readily recognized by those of skill in the art, altered antibodies (e.g., chimeric, humanized, CDR-grafted, bifunctional, antibody polypeptide dimers (i.e., an association of two polypeptide chain components of an antibody, e.g., one arm of an antibody including a heavy chain and a light chain, or an Fab fragment including VL, VH, CL and CH antibody domains, or an Fv fragment comprising a VL domain and a VH domain), single chain antibodies (e.g., an scFv (i.e., single chain Fv) fragment including a VL domain linked to a VH domain by a linker, and the like) can also be produced by methods well known in the art.

Monoclonal antibody (mAb) technology can be used to obtain mAbs to ROR1. Briefly, hybridomas are produced using spleen cells from mice immunized with ROR1 antigens. The spleen cells of each immunized mouse are fused with mouse myeloma Sp 2/0 cells, for example using the polyethylene glycol fusion method of Galfre, G. and Milstein, C., Methods Enzymol., 73:3-46 (1981). Growth of hybridomas, selection in HAT medium, cloning and screening of clones against antigens are carried out using standard methodology (Galfre, G. and Milstein, C., Methods Enzymol., 73:3-46 (1981)).

HAT-selected clones are injected into mice to produce large quantities of mAb in ascites as described by Galfre, G. and Milstein, C., Methods Enzymol., 73:3-46 (1981), which can be purified using protein A column chromatography (BioRad, Hercules, Calif.). mAbs are selected on the basis of their (a) specificity for ROR1, (b) high binding affinity, (c) isotype, and (d) stability.

mAbs can be screened or tested for ROR1 specificity using any of a variety of standard techniques, including Western Blotting (Koren, E. et al., Biochim. Biophys. Acta 876:91-100 (1986)) and enzyme-linked immunosorbent assay (ELISA) (Koren, E. et al., Biochim. Biophys. Acta 876:91-100 (1986)).

Humanized forms of mouse antibodies can be generated by linking the CDR regions of non-human antibodies to human constant regions by recombinant DNA techniques (see, e.g., Queen et al., Proc. Natl. Acad. Sci. USA 86:10029-10033, 1989 and WO 90/07861, each incorporated by reference). Human antibodies can be obtained using phage-display methods (see, e.g., Dower et al., WO 91/17271; McCafferty et al., WO 92/01047). In these methods, libraries of phage are produced in which members display different antibodies on their outer surfaces. Antibodies are usually displayed as Fv or Fab fragments. Phage displaying antibodies with a desired specificity may be selected by affinity enrichment.

Human antibodies may be selected by competitive binding experiments, or otherwise, to have the same epitope specificity as a particular mouse antibody. Using these techniques, a humanized ROR1 antibody having the human IgG1 constant region domain and the human kappa light chain constant region domain with the mouse heavy and light chain variable regions. The humanized antibody has the binding specificity of a mouse ROR1 mAb, specifically the 4A5 mAb described in Examples 4 and 5.

It may be desirable to produce and use functional fragments of a mAb for a particular application. The well-known basic structure of a typical IgG molecule is a symmetrical tetrameric Y-shaped molecule of approximately 150,000 to 200,000 daltons consisting of two identical light polypeptide chains (containing about 220 amino acids) and two identical heavy polypeptide chains (containing about 440 amino acids). Heavy chains are linked to one another through at least one disulfide bond. Each light chain is linked to a contiguous heavy chain by a disulfide linkage. An antigen-binding site or domain is located in each arm of the Y-shaped antibody molecule and is formed between the amino terminal regions of each pair of disulfide linked light and heavy chains. These amino terminal regions of the light and heavy chains consist of approximately their first 110 amino terminal amino acids and are known as the variable regions of the light and heavy chains. In addition, within the variable regions of the light and heavy chains there are hypervariable regions which contain stretches of amino acid sequences, known as complementarity determining regions (CDRs). CDRs are responsible for the antibody's specificity for one particular site on an antigen molecule called an epitope. Thus, the typical IgG molecule is divalent in that it can bind two antigen molecules because each antigen-binding site is able to bind the specific epitope of each antigen molecule. The carboxy terminal regions of light and heavy chains are similar or identical to those of other antibody molecules and are called constant regions. The amino acid sequence of the constant region of the heavy chains of a particular antibody defines what class of antibody it is, for example, IgG, IgD, IgE, IgA or IgM. Some classes of antibodies contain two or more identical antibodies associated with each other in multivalent antigen-binding arrangements.

Fab and F(ab′)₂ fragments of mAbs that bind ROR1 can be used in place of whole mAbs. Because Fab and F(ab′)₂ fragments are smaller than intact antibody molecules, more antigen-binding domains are available than when whole antibody molecules are used. Proteolytic cleavage of a typical IgG molecule with papain is known to produce two separate antigen binding fragments called Fab fragments which contain an intact light chain linked to an amino terminal portion of the contiguous heavy chain via by disulfide linkage. The remaining portion of the papain-digested immunoglobin molecule is known as the Fc fragment and consists of the carboxy terminal portions of the antibody left intact and linked together via disulfide bonds. If an antibody is digested with pepsin, a fragment known as an F(ab′)₂ fragment is produced which lacks the Fc region but contains both antigen-binding domains held together by disulfide bonds between contiguous light and heavy chains (as Fab fragments) and also disulfide linkages between the remaining portions of the contiguous heavy chains (Handbook of Experimental Immunology. Vol 1: Immunochemistry, Weir, D. M., Editor, Blackwell Scientific Publications, Oxford (1986)).

With respect to particular antibodies, “specific binding” refers to antibody binding to a predetermined antigen. Typically, the antibody binds with an affinity corresponding to a K_(D) of about 10⁻⁸ M or less, and binds to the predetermined antigen with an affinity (as expressed by K_(D)) that is at least 10 fold less, and preferably at least 100 fold less than its affinity for binding to a non-specific antigen (e.g., BSA, casein) other than the predetermined antigen or a closely-related antigen. Alternatively, the antibody can bind with an affinity corresponding to a K_(A) of about 10⁶ M⁻¹, or about 10⁷ M⁻¹, or about 10⁸ M⁻¹, or 10⁹M⁻¹ or higher, and binds to the predetermined antigen with an affinity (as expressed by K_(A)) that is at least 10 fold higher, and preferably at least 100 fold higher than its affinity for binding to a non-specific antigen (e.g., BSA, casein) other than the predetermined antigen or a closely-related antigen.

Also, reference to “an antibody having binding specificity for ROR-1 protein” includes antibody fragments having at least 90% or 95% sequence identity to any of the polypeptide sequences disclosed in SEQ ID NOs: 2, 4 6, 8, 12, 14, 16, 18 and 20, including variants modified by mutation to improve the utility thereof (e.g., improved ability to target specific cell types and the like). Such variants include those wherein one or more conservative substitutions are introduced into the heavy chain and/or the light chain of the antibody.

Such variants include those wherein one or more substitutions are introduced into the heavy chain nucleotide sequence and/or the light chain nucleotide sequence of the antibody. In some embodiments the variant has a light chain and/or heavy chain having a nucleotide sequence at least 80% or at least 90% or at least 95% identical to any of the nucleotide sequences set forth in SEQ ID NOs: 1, 3, 5, 7, 11, 13, 15, 17 and 19.

Polynucleotide sequences which code structural features of the antibodies of the invention include those whose sequences are set forth below. Each polynucleotide sequence is followed by the amino acid sequence of the encoded polypeptide. The light chain sequences which are considered to be “corresponding” to heavy chain sequences are those listed as being for the same antibody; i.e., the F2 heavy chain sequences correspond to the F2 light chain sequences, the D10 heavy chain sequences correspond to the D10 light chain sequences, and so forth.

SEQ ID NO: 1 4A5 Mouse Anti-ROR1 mAb Heavy Chain Variable Region Coding Sequence: GAAGTGAAACTGGTGGAGTCTGGGGGAGGCTTAGTGAAGCCTGGAGGGTC CCTGAAACTCTCCTGTGCAGCCTCTGGATT CACTTTCAGTAGCTATGCCATGTCTGGGTTCGCCAGATTCCAGAGAAGA GGCTGGAGTGGGTCGCATCCATTAGTCGTG GTGGTACCACCTACTATCCAGACAGTGTGAAGGGCCGATTCACCATCTCC AGAGATAATGTCAGGAACATCCTGTACCTG CAAATGAGCAGTCTGAGGTCTGAGGACACGGCCATGTATTACTGTGGAAG ATATGATTACGACGGGTACTATGCAATGGA CTACTGGGGTCAAGGAACCTCAGTCACCGTCTCCTCA SEQ ID NO: 2 4A5 Mouse Anti-ROR1 mAb Heavy Chain Variable Region Polypeptide Sequence: EVKLVESGGGLVKPGGSLKLSCAASGFTFSSYAMSWVRQIPEKRLEWVAS ISRGGTTYYPDSVKGRFTISRDNVRNILYL QMSSLRSEDTAMYYCGRYDYDGYYAMDYWGQGTSVTVSS SEQ ID NO: 3 4A5 Mouse Anti-ROR1 mAb Light Chain Variable Region Coding Sequence: GACATCAAGATGACCCAGTCTCCATCTTCCATGTATGCATCTCTAGGAGA GAGAGTCACTATCACTTGCAAGGCGAGTCC GGACATTAATAGCTATTTAAGCTGGTTCCAGCAGAAACCAGGGAAATCTC CTAAGACCCTGATCTATCGTGCAAACAGAT TGGTTGATGGGGTCCCATCAAGGTTCAGTGGCGGTGGATCTGGGCAAGAT TATTCTCTCACCATCAACAGCCTGGAGTAT GAAGATATGGGAATTTATTATTGTCTACAGTATGATGAATTTCCGTACAC GTTCGGAGGGGGGACCAAGCTGGAAATGAA AC SEQ ID NO: 4 4A5 Mouse Anti-ROR1 mAb Light Chain Variable Region Polypeptide Sequence: DIKMTQSPSSMYASLGERVTITCKASPDINSYLSWFQQKPGKSPKTLIYR ANRLVDGVPSRFSGGGSGQDYSLTINSLEY EDMGIYYCLQYDEFPYTFGGGTKLEMK SEQ ID NO: 5 F2, F12 and G6 Mouse Anti-ROR1 mAb  Heavy Chain Variable Region Coding Sequence: GAGGTCCAGCTACAGCAGTCTGGACCTGAGCTGGAGAAGCCTGGCGCTTC AGTGAAGATATCCTGCAAGGCTTCTGGTTT CGCATTCACTGGCTACAACATGAACTGGGTGAAACAGACCAATGGAAAGA GCCTTGAGTGGATTGGAAGTATTGATCCTT ACTATGGTGGTTCTACCTACAACCAGAAGTTCAAGGACAAGGCCACATTG ACTGTAGACAAATCCTCCAGCACAGCCTAC ATGCAACTCAAGAGCCTCACATCTGATGACTCTGCAGTCTATTACTGTGC AAGATCCCCGGGGGGGGACTATGCTATGGA CTACTGGGGTCAAGGAACCTCAGTCACCGTCTCCTCA SEQ ID NO: 6 F2, F12 and G6 Mouse Anti-ROR1 mAb  Heavy Chain Variable Region Polypeptide Sequence: EVQLQQSGPELEKPGASVKISCKASGFAFTGYNMNWVKQTNGKSLEWIGS IDPYYGGSTYNQKFKDKATLTVDKSSSTAY MQLKSLTSDDSAVYYCARSPGGDYAMDYWGQGTSVTVSS SEQ ID NO: 7 F2, F12 and G6 Mouse Anti-ROR1 mAb Light Chain Variable Region Coding Sequence: GACATCAAGATGACCCAGTCTCCATCTTCCATGTATGCATCTGTAGGAGA GAGAGTCACTATCACTTGTAAGGCGAGTCA GGGCATTAATAGCTATTCAGGCTGGTTCCAGCAGAAACCAGGGAAATCTC CTAAGACCCTGATTTATCGTGGAAATAGAT TGGTGGATGGGGTCCCATCAAGGTTCAGTGGCAGTGGATCTGGGCAAGAT TATTCTCTCACCATCAGCAGCCTGGAGTAT GAAGATATGGGAATTTATTATTGTCTACAGTATGATGAGTTTCCGTACAC GTTCGGAGGGGGGACCAAGCTGGAAATAAA AC SEQ ID NOs: 8 F2, F12 and G6 Mouse Anti-ROR1 mAb Light Chain Variable Region Polypeptide Sequence: DIKMTQSPSSMYASVGERVTITCKASQGINSYSGWFQQKPGKSPKTLIYR GNRLVDGVPSRFSGSGSGQDYSLTISSLEY EDMGIYYCLQYDEFPYTFGGGTKLEIK SEQ ID NO: 9 G3 Mouse Anti-ROR1 mAb Heavy Chain Variable Region Coding Sequence: CAGGTCCAACTGCAGCAGCCTGGGGCTGAGCTTGTGAAGCCTGGGACTTC AGTGAAGCTGTCCTGCAAGGCTTCTGGCTA CAACTTCACCAACTACTGGATAAACTGGGTGAAGCTGAGGCCTGGACAAG GCCTTGAGTGGATTGGAGAAATTTATCCTG GTAGTGGTAGTACTAATTACAATGAGAAGTTCAAGAGCAAGGCCACACTG ACTGCAGACACATCCTCCAGCACAGCCTAC ATGCAACTCAGCAGCCTGGCATCTGAAGACTCTGCTCTCTATTACTGTGC AAGAGATGGTAACTACTATGCTATGGACTA CTGGGGTCAAGGAACCTCAGTCACCGTCTCCTCA SEQ ID NO: 10 G3 Mouse Anti-ROR1 mAb Heavy Chain  Variable Region Polypeptide Sequence: QVQLQQPGAELVKPGTSVKLSCKASGYNFTNYWINWVKLRPGQGLEWIGE IYPGSGSTNYNEKFKSKATLTADTSSSTAY MQLSSLASEDSALYYCARDGNYYAMDYWGQGTSVTVSS SEQ ID NO: 11 G3 Mouse Anti-ROR1 mAb Light Chain  Variable Region Coding Sequence: GATATCCAGATGACACAGACTACATCCTCCCTGTCTGCCTCTCTGGGAGA CAGAGTCACCATCACTTGCAGGGCAAGTCA GGACATTAACAATTATTTAAACTGGTATCAACAGAAACCAGATGGAACTG TTAAACTCCTGATCTACTACACATCAGCAT TACACTCAGGAGTCCCATCAAGGTTCAGTGGCAGTGGGTCTGGAACAGAT TATTCTCTCACCATTAGCAACCTGGAACAA GAAGATATTGCCACTTACTTTTGCCAACAGGGTAATACGCTTCCTCCGTA CACGTTCGGAGGGGGGACCAAGCTGGAAAT AAAAC SEQ ID NO: 12 G3 Mouse Anti-ROR1 mAb Light Chain  Variable Region Polypeptide Sequence: DIQMTQTTSSLSASLGDRVTITCRASQDINNYLNWYQQKPDGTVKLLIYY TSALHSGVPSRFSGSGSGTDYSLTISNLEQ EDIATYFCQQGNTLPPYTFGGGTKLEIK SEQ ID NO: 13 D10 Mouse Anti-ROR1 mAb Heavy Chain Variable Region Coding Sequence: CAGGTGCAGCTGAAGGAGTCAGGACCTGGCCTGGTGGCGCCCTCACAGAC TCTGTCCATCACTTGCACTGTCTCTGGGTT TTCATTAACCAGTTATGGTGTACACTGGGTTCGCCAGCCTCCAGGAAAGG GTCTGGAGTGGCTGGGAGTAATATGGGCTG GTGGATTCACAAATTATAATTCGGCTCTCAAGTCCAGACTGAGCATCAGC AAAGACAACTCCAAGAGCCAAGTTCTCTTA AAAATGACCAGTCTGCAAACTGATGACACAGCCATGTACTACTGTGCCAG GAGAGGTAGTTCCTATTCTATGGACTATTG GGGTCAAGGAACCTCAGTCACCGTCTCCTCA SEQ ID NO: 14 D10 Mouse Anti-ROR1 mAb Heavy Chain  Variable Region Polypeptide Sequence QVQLKESGPGLVAPSQTLSITCTVSGFSLTSYGVHWVRQPPGKGLEWLGV IWAGGFTNYNSALKSRLSISKDNSKSQVLL KMTSLQTDDTAMYYCARRGSSYSMDYWGQGTSVTVSS SEQ ID NO: 15 D10 Mouse Anti-ROR1 mAb Light Chain  Variable Region Coding Sequence: GAAATTGTGCTCTCTCAGTCTCCAGCCATCACAGCTGCATCTCTGGGCCA AAAGGTCACCATCACCTGCAGTGCCAGTTC AAATGTAAGTTACATCCACTGGTACCAGCAGAGGTCAGGCACCTCCCCCA GACCATGGATTTATGAAATATCCAAACTGG CTTCTGGAGTCCCAGTTCGCTTCAGTGGCAGTGGGTCTGGGACCTCTTAC TCTCTCACAATCAGCAGCATGGAGGCTGAA GATGCTGCCATTTATTATTGTCAGCAGTGGAATTATCCTCTTATCACGTT CGGCTCGGGGACAAAGTTGGAAATACAA SEQ ID NO: 16 D10 Mouse Anti-ROR1 mAb Light Chain  Variable Region Polypeptide Sequence: EIVLSQSPAITAASLGQKVTITCSASSNVSYIHWYQQRSGTSPRPWIYEI SKLASGVPVRFSGSGSGTSYSLTISSMEAE DAAIYYCQQWNYPLITFGSGTKLEIQ SEQ ID NO: 17 H10 and G11 Mouse Anti-ROR1 mAb  Heavy Chain Variable Region Coding Sequence: GAAGTGAAGCTGGTGGAGTCTGGGGGAGGCTTAGTGAAGCCTGGAGGGTC CCTGAAACTCTCCTGTGCAGCCTCTGGATT CACTTTCAGTAGCTATGCCATGTCTGGGTTCGCCAGACTCCAGAGAAGA GGCTGGAGTGGGTCGCTTCCATTAGTACTG GTGCTAGCGCCTACTTTCCAGACAGTGTGAAGGGCCGATTCACCATCTCC AGAGATAATGCCAGGAACATCCTGTACCTG CAAATGAGCAGTCTGAGGTCTGAGGACACGGCCATGTATTATTGTGCAAG GATTACTACGTCTACCTGGTACTTCGATGT CTGGGGCGCAGGGACCACGGTCACCGTCTCCTCA SEQ ID NO: 18 H10 and G11 Mouse Anti-ROR1 mAb  Heavy Chain Variable Region Polypeptide Sequence: EVKLVESGGGLVKPGGSLKLSCAASGFTFSSYAMSWVRQTPEKRLEWVAS ISTGASAYFPDSVKGRFTISRDNARNILYL QMSSLRSEDTAMYYCARITTSTWYFDVWGAGTIVIVSS SEQ ID NO: 19 H10 and G11 Mouse Anti-ROR1 mAb  Light Chain Variable Region Coding Sequence: GACATCAAGATGACCCAGTCTCCATCTTCCATGTATGCATCTCTAGGAGA GAGAGTCACTATCACTTGCAAGGCGAGTCA GGACATTAATAGTTATTTAAGCTGGTTCCAGCAGAAACCAGGGAAATCTC CTAAGACCCTGATCTATCGTGCAAACAGAT TGGTAGATGGGGTCCCATCAAGGTTCAGTGGCAGTGGATCTGGGCAAGAT TATTCTCTCACCATCAGCAGCCTGGAGTAT GAAGATATGGGAATTTATTATTGTCTACAGTATGATGAGTTTCCGTACAC GTTCGGAGGGGGGACCAAGCTGGAAATAAA AC SEQ ID NO: 20 H10 and G11 Mouse Anti-ROR1 mAb  Light Chain Variable Region Polypeptide Sequence: DIKMTQSPSSMYASLGERVTITCKASQDINSYLSWFQQKPGKSPKTLIYR ANRLVDGVPSRFSGSGSGQDYSLTISSLEY EDMGIYYCLQYDEFPYTFGGGTKLEIK

In one aspect, antibodies are provided in which a heavy chain encoded by the polynucleotide sequence of SEQ ID NO:13 and a light chain encoded by the polynucleotide sequence of SEQ ID NO:15.

In another aspect, an antibody of the present invention contains a heavy chain encoded by the polynucleotide sequence of SEQ ID NO:1 and a light chain encoded by the polynucleotide sequence of SEQ ID NO:3.

In further aspects, antibodies are provided which have a heavy chain encoded by the polynucleotide sequence of SEQ ID NO: 5 and a light chain encoded by the polynucleotide sequence of SEQ ID NO: 7; or by the polynucleotide sequence of SEQ ID NO: 9 and a light chain encoded by the polynucleotide sequence of SEQ ID NO: 11; or by the polynucleotide sequence of SEQ ID NO: 15 and a light chain encoded by the polynucleotide sequence of SEQ ID NO: 17.

In another aspect, antibodies are provided which contain a heavy chain with the polypepetide sequence of SEQ ID NO:14 and a light chain with the polypeptide sequence of SEQ ID NO:16.

In another aspect, antibodies are provided which contain a heavy chain with the polypeptide sequence of SEQ ID NO:2 and a light chain with the polypeptide sequence of SEQ ID NO:4.

In one embodiment, isolated polynucleotides which encode an antibody that specifically binds ROR1 protein are provided which are (a) comprised of a heavy chain region coded by polynucleotides having at least 90% sequence identity with any of the sequences selected from the group consisting of SEQ ID NOs: 1, 5, 9, 13 or 17, (b) comprised of a corresponding light chain region encoded by polynucleotides having at least 90% sequence identity with any of the sequences selected from the group consisting of SEQ ID NOs: 3, 7, 11, 15 or 19, and (c) specifically binds either the 3′ end or middle portion of the Ig-like region of the extracellular domain of human or murine ROR-1 protein.

Also provided are antibodies which bind residues within the middle of the Ig-like region of the extracellular domain of human or murine ROR-1 protein (amino acids 1-147 in the human molecule). In one aspect, the antibodies of the present invention bind to amino acids 70-130 of human ROR1. Examples of such antibodies include 4A5, G11, H10 and G3.

Alternatively or additionally, a residue corresponding to the one found in the extracellular domain of human ROR-1 protein at position 111 is critical to the binding activity of the antibodies.

Further provided are antibodies that bind residues within the 3′ Ig-like region and the linker region between the Ig-like domain and the CRD domain of human or murine ROR-1 protein (amino acids 1-165 in the human molecule). In one aspect, the antibodies of the present invention bind to amino acids 130-165 of human ROR1. Examples of such antibodies include D10, F2, F12 and G6.

Alternatively or additionally, the antibodies bind a glutamic acid residue corresponding to the one found in the extracellular domain of human ROR-1 protein at position 138.

Alternatively or additionally, a residue corresponding to the one found in the extracellular domain of human ROR-1 protein at position 138 is critical to the binding activity of the antibodies.

Alternatively or additionally, the encoded antibody has in vivo activity in reducing leukemic or lymphomic cell burden in an art-accepted animal model at a rate of 2-8 times, or at least 2, 3, 4, 5, 6, 7, or 8 times, that of wild-type human anti-ROR1 antibody or monoclonal 4A5 antibody (disclosed herein).

Alternatively or additionally, the encoded antibody has in vivo activity in inhibiting CD5^(dull)B220⁺ and ROR1^(bright)B220⁺ leukemic B cell expansion.

Alternatively or additionally, the encoded antibody is internalized into leukemic or lymphomic cells at a rate of at least 2 times, or at least 2, 3, 4, 5, 6, 7, 8, 9 or 10 times that of monoclonal antibody 4A5. Such antibodies are particularly useful as carriers for drug delivery into a targeted cell.

An example of an antibody possessing all of the a fore-mentioned functional characteristics is D10, which has a heavy chain region encoded by SEQ ID NO: 13 and a light chain region encoded by SEQ ID NO: 15.

In another aspect, polypeptides are provided which consist of or comprise antibodies which specifically bind ROR1 protein and are (a) comprised of a heavy chain region having at least 90% sequence identity with any of the sequences of SEQ. ID. NOs: 2, 6, 10, 14 or 18, (b) comprised of a corresponding light chain region having at least 90% sequence identity with any of the sequences of SEQ ID NOs: 4, 8, 12, 16 or 20, and (c) specifically binds either the 3′ end or middle portion of the Ig-like region of the extracellular domain of human or murine ROR-1 protein. In one aspect, the isolated polypeptide is an antibody. In a further aspect, the polypeptide is a Fab or F(ab)′2.

In certain embodiments, an antibody of the present invention may further contain a detectable label. Such labels are known in the art and include radio-isotopes and fluorescent labels. As such, internalization of a compound evidencing passage through transporters can be detected by detecting a signal from within a cell from any of a variety of reporters. The reporter can be a label such as a fluorophore, a chromophore, a radioisotope. Confocal imagining can also be used to detect internalization of a label as it provides sufficient spatial resolution to distinguish between fluorescence on a cell surface and fluorescence within a cell; alternatively, confocal imaging can be used to track the movement of compounds over time. In another approach, internalization of a compound is detected using a reporter that is a substrate for an enzyme expressed within a cell. Once the complex is internalized, the substrate is metabolized by the enzyme and generates an optical signal or radioactive decay that is indicative of uptake. Light emission can be monitored by commercial PMT-based instruments or by CCD-based imaging systems. In addition, assay methods utilizing LCMS detection of the transported compounds or electrophysiological signals indicative of transport activity are also employed.

In certain therapeutic embodiments, the selected antibody may be administered alone, in combination with another antibody of the invention, or with one or more combinatorial therapeutic agents to treat an ROR-1 cancer. When one or more the antibodies described herein are administered as therapeutic agents, they may exert a beneficial effect in the subject by a variety of mechanisms. For example, in certain embodiments, antibodies that specifically bind ROR1 are purified and administered to a patient to neutralize one or more forms of ROR1, to block one or more activities of ROR1, or to block or inhibit an interaction of one or more forms of ROR1 with another biomolecule; e.g., to treat CLL or other ROR1 cancers. All such therapeutic methods are practiced by delivery of a therapeutically effective dosage of a pharmaceutical composition containing the therapeutic antibodies and agents, which can be determined by a pharmacologist or clinician of ordinary skill in human cancer immunotherapy.

In one embodiment, the present invention provides for a method for of treating cancer by the administration to a human subject in need thereof of a therapeutically effective dose of an antibody according to the invention.

In another embodiment, the present invention provides a method for of treating cancer comprising administration to a human subject in need thereof of a therapeutically effective dose of an antibody according to the invention.

Advantageously, the methods of the invention provide for reduction of leukemic or lymphomic cell burden (as demonstrated in and equivalent to an art-accepted animal model) of 2-8 times, or at least 2, 3, 4, 5, 6, 7, or 8 times, that of wild-type human anti-ROR1 antibody or monoclonal 4A5 antibody (disclosed herein).

The methods of the invention further provide a therapeutic approach to inhibiting CD5^(dull)B220⁺ and ROR1^(bright)B220⁺ leukemic B cell expansion.

As discussed herein, the antibodies of the invention may include humanized antibodies, and can be combined for therapeutic use with additional active or inert ingredients, e.g., in conventional pharmaceutically acceptable carriers or diluents, e.g., immunogenic adjuvants, and optionally with adjunctive or combinatorially active molecules such as anti-inflammatory and anti-fibrinolytic drugs. Antibodies which readily internalize into cells as demonstrated herein with respect to the D10 antibody are also of particular use as carriers for drug delivery into target cells (for example, as shown in FIGS. 21-23). Those of ordinary skill in the art will be familiar with methods for producing antibody-drug conjugates useful in such drug delivery protocols.

In carrying out various assay, diagnostic, and therapeutic methods of the invention, it is desirable to prepare in advance kits comprises a combination of antibodies as described herein with other materials. For example, in the case of sandwich enzyme immunoassays, kits of the invention may contain an antibody that specifically binds ROR1 optionally linked to an appropriate carrier, a freeze-dried preparation or a solution of an enzyme-labeled monoclonal antibody which can bind to the same antigen together with the monoclonal antibody or of a polyclonal antibody labeled with the enzyme in the same manner, a standard solution of purified ROR1, a buffer solution, a washing solution, pipettes, a reaction container and the like. In addition, the kits optionally include labeling and/or instructional materials providing directions (i.e., protocols) for the practice of the methods described herein in an assay environment. While the instructional materials typically comprise written or printed materials, they are not limited to such. Any medium capable of storing such instructions and communicating them to an end user is contemplated. Such media include, but are not limited to electronic storage media (e.g., magnetic discs, tapes, cartridges, chips), optical media (e.g., CD ROM), and the like. Such media may include addresses to internet sites that provide such instructional materials.

In general, an in vitro method of diagnosing a ROR-1 cancer will comprise contacting putative cancer cells from a human subject with an antibody according to the invention, and detecting binding with ROR-1 expressed on said cells as compared to expression on post-embryonic human non-cancer cells. All such diagnostic methods are practiced by delivery of a diagnostically effect quantity of antibodies according to the invention, which can be determined by a diagnostician or in vitro diagnostic engineer of ordinary skill in human cancer diagnosis.

The following examples are intended to illustrate but not limit the invention.

Example 1: Generation of Monoclonal Anti-ROR1 Antibodies

For the production of the hybridoma-generated mAbs, mice were inoculated with DNA, protein and adenoviral constructs that express the extracellular portion (AA 1-406) of the ROR1 protein that include the Ig-like, CRD and Kringle domains and adjacent linker regions (FIGS. 10-11). Because of the high degree of homology between the murine and human molecules, a variety of cytokines and immune stimulatory agents, such as Freund's Complete Adjuvant, were co-injected to maximize the generation of anti-human ROR1 antibodies. Hybridoma-generated mAbs were generated and screened for binding to human and murine ROR1. An example of hybridoma derived mAbs is D10.

Example 2: Generation of Anti-ROR1 Antibodies Using Phage Display

A second set of antibodies was generated through the use of a proprietary enhanced phage library (Alere, Inc. San Diego). These anti-human ROR1 antibodies bind epitopes that span the entire length of the extra-cellular domain of the ROR1 protein (FIG. 12). An example of a phage display derived anti-ROR1 antibody is 4A5.

Example 3: In Vitro Analysis of Anti-ROR1 Antibodies

Antibodies generated through either hybridomas or phage display were screened for binding to human and murine ROR1. It was determined that the anti-ROR1 antibodies D10 and 4A5 bound only to human ROR1 and did not cross react with murine ROR1.

Example 4: Determination of Binding Sites for Anti-ROR1 Antibodies

Because the anti-ROR1 mAbs are species specific, a series of chimeric proteins were generated that were used to determine the binding site for each of the anti-ROR1 mAbs (FIG. 13). As a second level screen, a series of deletion constructs were generated to determine the actual extracellular ROR1 domain to which the mAbs bind. Once the binding domain was identified, truncated chimeric ROR1 molecules to identify specific sub-regions were generated that are recognized by the anti-human ROR1 mAbs (FIG. 14). As a final step, the actual amino acids targeted by these antibodies were determined. For this final screen, murinized human amino acids in the sub-domain fragments were generated to determine critical residues required for mAb binding (FIG. 15). From this screening paradigm, the binding sub-domains for the mAbs were determined (FIG. 15). It was determine that the D10 anti-human ROR1 mAb required the glutamic acid residue at position 138 for binding to the Ig-like domain of the human ROR1 molecule. When this amino acid is replaced with the murine molecule's lysine residue, the D10 molecule no longer bound to the ROR1 protein.

In a similar manner, it was determined that 4A5 anti-human ROR1 mAb required the isoleucine residue at position 111 for binding to human ROR1 molecule (FIG. 24). When this amino acid is replaced with the murine molecule's asparagine residue, the 4A5 molecule no longer bound to the ROR1 protein. It was also determined that the anti-ROR1 antibodies G11, H10 and G3 bind the same region as 4A5.

Using standard cross blocking techniques the binding sites for anti-ROR1 antibodies F2, F12 and G6 were determined. These experiments determined that antibodies F2, F12 and G6 cross block the anti-ROR1 antibody D10, indicating that they share a binding site.

Example 5: Determination of the K_(D) Values for the Anti-ROR1 Antibodies D10 and 4A5

The K_(D) values for the anti-ROR1 antibodies was determined using standard techniques. It was determined that the K_(D) for the D10 antibody was 40 nM and for the antibody 4A5 was 4 nM (FIGS. 16A-16B).

Example 6: In Vivo Analysis of Anti-ROR1 Antibodies

The D10 mAb was assessed in several in vivo models. In a murine in vivo xenograph, niche-dependent, activity model two doses of the mAb were administered at 10 mg/kg against 4 primary patient CLL cells in 76 mice. As shown in FIG. 17, D10 mAb substantially eliminated patient CLL cells in a dose dependent manner. In contrast, the 4A5 mAb had minimal activity in these studies even though the kDa of this mAb is 10 fold greater (4 vs. 40) for the D10 mAb.

In addition to this activity model, the D10 mAb was also tested in an immune competent transgenic mouse model that spontaneously generates leukemic cells expressing the human ROR1 protein (FIGS. 18-20). The ROR1-specific mAbs D10 and 4A5 or control IgG antibodies (10 mg/kg) were administered before and after adoptive transfer of ROR1×TCL1 CLL B cells into Balb C mice. The D10 mAb, but not control IgG or 4A5, was able to inhibit the development and expansion of the ROR1×TCL1 leukemic B cells in the blood of recipient animals until two weeks after receiving the last infusion of MAb.

Along with the anti-leukemic activity of this mAb, it has also been shown that the D10 anti-ROR1 antibody is internalized into patient CLL cells and B cell leukemia and lymphoma cell lines at a greater rate and degree than other anti-ROR1 MAbs that bind other antigenic sites on the extracellular portion of the ROR1 protein (FIGS. 21-23). Because of the absence of the ROR1 protein on post-partum tissues and its rapid rate of internalization, the D10 mAb may serve as an excellent carrier protein for drugs; for example, for use in directed antibody-drug conjugate (ADC) mediated cytotoxicity. Based on these preclinical findings, the D10 mAb has potential to have therapeutic activity against ROR1 expressing leukemias, lymphomas and solid tumor cancers as a targeted therapy and/or conjugated drug carrier.

Although the foregoing subject matter has been described in some detail by way of illustration and example for purposes of clarity of understanding, it will be understood by those skilled in the art that certain changes and modifications can be practiced within the scope of the appended claims. 

What is claimed is:
 1. A method of identifying an anti-ROR1 antibody, the method comprising: (i) contacting an antibody with a first ROR1 polypeptide comprising amino acid residues 1-147 of SEQ ID NO:36; (ii) detecting said antibody binding to said first ROR1 polypeptide; (iii) contacting said antibody with a second ROR 1 polypeptide comprising amino acid residues 1-147 of SEQ ID NO:37 or amino acid residues 1-147 of SEQ ID NO:36, wherein the glutamic acid residue at position 138 of SEQ ID NO:36 is replaced by lysine; and (iv) detecting said antibody not binding to said second ROR1 polypeptide, thereby identifying an anti-ROR1 antibody.
 2. The method of claim 1, wherein said first ROR1 polypeptide is a truncated ROR1 polypeptide.
 3. The method of claim 2, wherein said truncated ROR1 polypeptide comprises amino acid residues 1-165 of SEQ ID NO:36.
 4. The method of claim 1, wherein said second ROR1 polypeptide is a truncated ROR1 polypeptide.
 5. The method of claim 4, wherein said truncated ROR1 polypeptide comprises amino acid residues 1-165 of SEQ ID NO:37.
 6. The method of claim 1, wherein said antibody is a humanized antibody.
 7. The method of claim 1, wherein said antibody is an antibody fragment.
 8. The method of claim 1, wherein said antibody is a chimeric antibody.
 9. The method of claim 1, wherein said antibody is a single chain antibody.
 10. The method of claim 1, wherein said antibody binds to said first ROR1 polypeptide with a K_(D) of less than 40 nM.
 11. The method of claim 1, wherein said antibody binds to said first ROR1 polypeptide with a K_(D) of about 40 nM. 